Current status of fish diversity and parasites of fish in Krasnoyarsk Reservoir

Regulation of the Yenisei River basin has resulted in the appearance of an entirely new hydrologi-cal, hydrochemical, hydrobiological characteristics. The species composition and ichthyocenosis structure has changed under the new conditions. Biological productivity generally increases. About 30 species of fish and agnathous lived in the flood zone before the reservoir was created. Rheophilic forms were the base of ichthyocenosis (60%). The most numerous species were represented by dace, roach, perch, starlet and taimen. Currently only 25 species of fish and 1 species of agnathous inhabit the Krasnoyarsk Reservoir. The ichthy-ofauna diversity of the reservoir was due to the fishes in the Yenisei River mainstream, tributaries, ducts and partially to the immigrants from the lakes of the flood zone. In fact, the fishes of the Upper Yenisei were preserved and redistributed in the waters of the pond. As a result of spontaneous settlement three species (carp, verkhovka, trout) appeared in the lake, two species (cisco, peled) appeared due to the formation of pasture aquaculture and one species appeared during acclimatization (bream). Acclimatized species fully naturalized are represented by bream, carp and verkhovka (non-target species). All of them have formed self-reproducing populations. Baikal cisco and peled do not form self-reproducing populations and exist due to the constant immigration of young of the fishes. Over the last twenty years, preferential development is provided to the fish with rapid reproductive potential, with lack of food specialization and indifference to the spawning substrate and dragged spawning or summer spawning with deficiency in providing spawning areas and underde-velopment of prey. The process of parasite fauna formation apparently took place in three stages, similar to most reservoirs, meanwhile each stage was characterized by significant changes in the structure of the parasite-fauna. The first stage represents the destruction of the rheophilic complex due to the loss or reduction of the maximum number of their intermediate and definitive hosts and the beginning of the formation of the limnophilic complex, whose members are related in their development to limnophilic fish. The second stage was characterized by stabilization of the number and species of parasites. The third stage is represented by change in the parasites due to the introduction and distribution of a range of new species of fish, abiotic factors and anthropogenic impact on the pond. At present, fish of the Krasnoyarsk Reservoir are represented by 31 species of parasitic organisms, cestodes dominate in species diversity and extensive-ness, trematodes and peritrichous bacteria dominate in numbers. In general, the formation of parasite fauna of fishes in the Krasnoyarsk Reservoir can be considered complete in its basic features, characteristic for this type of reservoir diseases: bothriocephaliasis, trie-aenophorus, ligula and ergasilus infections.

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